Apple continues to show interest in using hydrogen fuel cell technology, as evidenced in its latest patent filing. On Thursday, the United States Patent and Trademark Office published a patent titled “Fuel Cell System to Power a Portable Computing Device.”

The invention appears to be, at least initially, targeted at the MacBook, as the filing mentions MagSafe several times. But last month, the British firm Intelligent Energy proved the tech can be shrunken down, by showing off an iPhone with a hydrogen fuel cell.

Apple outlines several benefits of its fuel cell invention, including its ability to significantly expand battery life in mobile devices. In one specific portion of the application, the inventors suggest it could enable devices to go “days or even weeks” between refueling.

Of course there are some caveats to the tech as well, such as users having to manually replace the fuel once it is depleted, though Apple said this could be remedied by cartridges. And there are also concerns regarding mass manufacturing and environmental impact.

Keep in mind that Apple has patented tens of thousands of ideas and inventions in the past, which never made it into actual products. But given that its current lineup of mobile devices can barely last a day, I imagine a lot of users are hoping that won’t be the case here.